The present invention relates to a device for removing insulation from the end of an insulated electrical wire and, more particularly, to such a device which allows the insulation to be removed from the wire without skiving of the wire.
In a typical insulation stripping apparatus such as disclosed in U.S. Pat. No. 3,893,776 to Anderson, et al., assigned to the assignee of the present application, there are provided two stripper blades, one of which is fixed and the other movable. In the Anderson apparatus, the movable blade is pivotably mounted. Each blade has a V-shaped notch therein facing the notch of the other blade. One surface of each blade adjacent to the notch is flat while the other surface is formed with a bevel. The beveled surfaces on the respective blades face in opposite directions. As a result, it is possible that when the insulation is stripped from a wire inserted into the opening defined by the V-shaped notches, the wire will skive or bend due to the unbalanced forces acting on the opposite sides of the wire. A bent wire prevents proper positioning of the wire in a contact crimp barrel so that it is possible that the barrel may not be properly crimped upon the end of the wire. Thus, one object of the present invention is to provide a stripper blade assembly for an insulation stripping device in which the beveled edges of the stripper blades are balanced so that a uniform cutting action is produced on the insulation whereby the wire will not skive when the insulation is removed therefrom.
Typically, the cutting edges of the V-shaped notch in the cutting blade of a conventional insulation stripper form a right angle so that the opening formed by the notches in the blades into which the wire is inserted for stripping has a square shape. If one of the blades is carried by a pivoted arm, and the other blade is fixed, the movable blade will move through an arc. As a result, when the size of the opening is altered by adjusting one of the blades, the configuration of the opening may become non-uniform, rather than form a square, which will result in further unbalanced forces acting upon the insulation on the wire by the blades. Furthermore, with one blade fixed and the other movable, the center of the opening defined by the notches in the blades will change if the size of the opening is altered by adjusting one of the blades so that when a wire is inserted through a central guide hole in front of the blade assembly, the wire may not necessarily lie in the center of the opening formed by the notches in the blades, further leading to unbalanced forces being applied to the opposite sides of the insulation on the wire. It is another object of the present invention to overcome the foregoing problem by assuring that the wire receiving opening defined by the blades is always square, and the center point of the opening remains constant regardless of adjustments being made to the blades to alter the size of the wire receiving opening to accommodate different sized wires.
As will be seen from the following description, the stripping device of the present invention utilizes four insulation cutting blades. The use of more than two cutting blades in a wire stripping machine is not by itself novel. For example, the following United States patents disclose wire stripping machines utilizing either three or four blades. U.S. Pat. Nos. 2,239,755; 2,703,026; 4,116,092 and 4,327,609. The latter patent discloses a wire stripping machine incorporating two pairs of insulation cutting blades, with one pair of opposed blades overlapping the other pair adjacent to their cutting edges. The blades are attached by screws to internal and external cylinders so that when one cylinder is rotated relative to the other, the cutting edges of the blades move inwardly to cut the insulation on the wire inserted between the inner ends of the blades.